Artificial light at night may increase risk of diabetes

 

New study reveals that exposure to outdoor artificial light at night is associated with an increased risk of diabetes

Date:

November 14, 2022

Source:

Diabetologia

Summary:

A new study finds that outdoor artificial light at night (LAN) is associated with impaired blood glucose control and an increased risk of diabetes, with more than 9 million cases of the disease in Chinese adults being attributed to LAN exposure.

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Exposure to artificial LAN at night is a ubiquitous environmental risk factor in modern societies. The intensity of urban light pollution has increased to the point that it not only affects residents of big cities, but also those in distant areas such as suburbs and forest parks that may be hundreds of kilometres from the light source. The authors note: "Despite over 80% of the world's population being exposed to light pollution at night, this problem has gained limited attention from scientists until recent years."

Earth's 24-hour day-night cycle has resulted in most organisms, including mammals, having an inbuilt circadian (roughly 24-hour) timing system which is adapted to the natural sequence of light and dark periods. Light pollution has been found to alter the circadian rhythm of insects, birds and other animals, resulting in premature death and loss of biodiversity.

Artificial LAN has also been implicated as a potential cause of metabolic dysregulation through altering the timing of food intake. Rats exposed to artificial LAN developed glucose intolerance, exhibiting elevated blood sugar and insulin. Another study found that mice exposed to nocturnal dim white light of minimal brightness for 4 weeks had increased body mass and reduced glucose tolerance compared to animals whose environment was completely dark at night, despite having roughly equivalent energy consumption and expenditure.

Associations have also been found between artificial LAN and health problems in humans. A study of night-shift workers found that those exposed to brighter LAN were more likely to have disrupted circadian rhythms, as well as a greater risk of coronary heart disease. Other research found that higher LAN exposure was associated with a 13% and 22% increase in the likelihood of being overweight and obese, respectively, while exposure to LAN in the bedroom was reported to be positively associated with the development of diabetes in elderly people.

The potential impact of outdoor artificial LAN was revealed by a study in South India which used satellite images to map light pollution and compared this with data on general health markers among adults across the region. With increasing LAN intensity, there were corresponding rises in average body mass index (BMI), systolic blood pressure and 'bad' (LDL) cholesterol levels in the exposed population.

Diabetes is a critical public health problem in China, and the onset and progression of the disease is largely governed by behavioural and environmental risk factors. The nation's rapid urbanisation and economic growth has resulted in a dramatic increase in urban lighting, and the number of people exposed to it. Those living in cities are prone to being shifted away from a natural 24-hour day-night cycle, to one of round-the-clock working and leisure time, often staying out late and being exposed to artificial LAN.

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Close the blinds during sleep to protect your health

Even moderate light exposure during sleep harms heart health and increases insulin resistance

Bedroom with full moon | Credit: © Brilliant Eye / stock.adobe.com

Summary:

Exposure to even moderate ambient lighting during nighttime sleep, compared to sleeping in a dimly lit room, harms your cardiovascular function during sleep and increases your insulin resistance the following morning, reports a new study. Just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes and metabolic syndrome.

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Close the blinds, draw the curtains and turn off all the lights before bed. Exposure to even moderate ambient lighting during nighttime sleep, compared to sleeping in a dimly lit room, harms your cardiovascular function during sleep and increases your insulin resistance the following morning, reports a new Northwestern Medicine study

"The results from this study demonstrate that just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes and metabolic syndrome," said senior study author Dr. Phyllis Zee, chief of sleep medicine at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician. "It's important for people to avoid or minimize the amount of light exposure during sleep."

There is already evidence that light exposure during daytime increases heart rate via activation of the sympathetic nervous system, which kicks your heart into high gear and heightens alertness to meet the challenges of the day.

"Our results indicate that a similar effect is also present when exposure to light occurs during nighttime sleep," Zee said.

Heart rate increases in light room, and body can't rest properly

"We showed your heart rate increases when you sleep in a moderately lit room," said Dr. Daniela Grimaldi, a co-first author and research assistant professor of neurology at Northwestern. "Even though you are asleep, your autonomic nervous system is activated. That's bad. Usually, your heart rate together with other cardiovascular parameters are lower at night and higher during the day."

There are sympathetic and parasympathetic nervous systems to regulate our physiology during the day and night. Sympathetic takes charge during the day and parasympathetic is supposed to at night, when it conveys restoration to the entire body.

How nighttime light during sleep can lead to diabetes and obesity

Investigators found insulin resistance occurred the morning after people slept in a light room. Insulin resistance is when cells in your muscles, fat and liver don't respond well to insulin and can't use glucose from your blood for energy. To make up for it, your pancreas makes more insulin. Over time, your blood sugar goes up.

An earlier study published in JAMA Internal Medicine looked at a large population of healthy people who had exposure to light during sleep. They were more overweight and obese, Zee said.

"Now we are showing a mechanism that might be fundamental to explain why this happens," Zee said. "We show it's affecting your ability to regulate glucose."

The participants in the study weren't aware of the biological changes in their bodies at night.

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"But the brain senses it," Grimaldi said. "It acts like the brain of somebody whose sleep is light and fragmented. The sleep physiology is not resting the way it's supposed to."

Exposure to artificial light at night during sleep is common

Exposure to artificial light at night during sleep is common, either from indoor light emitting devices or from sources outside the home, particularly in large urban areas. A significant proportion of individuals (up to 40%) sleep with a bedside lamp on or with a light on in the bedroom and/or keep the television on.

Light and its relationship to health is double edged.

"In addition to sleep, nutrition and exercise, light exposure during the daytime is an important factor for health, but during the night we show that even modest intensity of light can impair measures of heart and endocrine health," Zee said.

The study tested the effect of sleeping with 100 lux (moderate light) compared to 3 lux (dim light) in participants over a single night. The investigators discovered that moderate light exposure caused the body to go into a higher alert state. In this state, the heart rate increases as well as the force with which the heart contracts and the rate of how fast the blood is conducted to your blood vessels for oxygenated blood flow.

"These findings are important particularly for those living in modern societies where exposure to indoor and outdoor nighttime light is increasingly widespread," Zee said.

Zee's top tips for reducing light during sleep

(1) Don't turn lights on. If you need to have a light on (which older adults may want for safety), make it a dim light that is closer to the floor.

(2) Color is important. Amber or a red/orange light is less stimulating for the brain. Don't use white or blue light and keep it far away from the sleeping person.

(3) Blackout shades or eye masks are good if you can't control the outdoor light. Move your bed so the outdoor light isn't shining on your face.

Is my room too light?

"If you're able to see things really well, it's probably too light," Zee said.

Story Source:

Materials provided by Northwestern University. Original written by Marla Paul. Note: Content may be edited for style and length.

Diabetes and Coronavirus, CO-VID19

Take charge of your health.

• COVID-19 & diabetes

The COVID-19 outbreak has been declared an international public health emergency. People with diabetes may be more vulnerable to the severe effects of the virus.

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COVID-19 is a new and potentially serious coronavirus. There are many coronaviruses, ranging from the common cold to much more serious viruses such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS). They are viruses that have been transmitted from animals to people. In severe cases, coronaviruses can cause infection in the lungs (pneumonia), kidney failure and even death.

The World Health Organization (WHO) has declared the COVID-19 outbreak to be a public health emergency of international concern. At present there is no vaccine against COVID-19.

Common signs are typical flu-like symptoms: a fever, cough, breathing difficulties, tiredness and muscle aches. Symptoms usually start within 3-7 days of exposure to the virus, but in some cases it has taken up to 14 days for symptoms to appear.

People of all ages can be infected. For many (more than 80% of cases), COVID-19 is mild, with minimal flu-like symptoms. Some have not shown symptoms or only very mild symptoms, more like a common cold. The majority of people who have caught the virus did not need to be hospitalised for supportive care. However, in approaching 15% of cases COVID-19 has been severe and in around 5% of cases it has led to critical illness. The vast majority (around 98%) of people infected to date have survived.

When people with diabetes develop a viral infection, it can be harder to treat due to fluctuations in blood glucose levels and, possibly, the presence of diabetes complications.

Older people and people with pre-existing medical conditions (such as diabetes, heart disease and asthma) appear to be more vulnerable to becoming severely ill with the COVID-19 virus. When people with diabetes develop a viral infection, it can be harder to treat due to fluctuations in blood glucose levels and, possibly, the presence of diabetes complications. There appear to be two reasons for this. Firstly, the immune system is compromised, making it harder to fight the virus and likely leading to a longer recovery period. Secondly, the virus may thrive in an environment of elevated blood glucose.

Like any other respiratory disease, COVID-19 is spread through air-droplets that are dispersed when an infected person talks, sneezes or coughs. The virus can survive from a few hours up to a few days depending on the environmental conditions. It can be spread through close contact with an infected person or by contact with air droplets in the environment (on a surface for example) and then touching the mouth or nose (hence the common advice circulating on hand hygiene and social distancing).

What can people with diabetes and their loved ones do?

For people living with diabetes it is important to take precautions to avoid the virus if possible. The recommendations that are being widely issued to the general public are doubly important for people living with diabetes and anyone in close contact with people living with diabetes.

• Wash hands thoroughly and regularly.
• Try to avoid touching your face before you have washed and dried your hands.
• Clean and disinfect any objects and surfaces that are touched frequently.
• Don’t share food, glasses, towels, tools etc.
• When you cough or sneeze, cover your mouth and nose with a tissue or use the crook of your arm if you don’t have a tissue to hand (dispose of the tissue appropriately after use).
• Try to avoid contact with anyone showing symptoms of respiratory illness such as coughing.
• Think whether you can make changes that will help protect yourself or loved ones. For example, can you avoid unnecessary business travel? Can you avoid large gatherings? Can you avoid public transport?
• If you are ill with flu-like symptoms, stay at home.

If you have diabetes:

• Prepare in case you get ill.
• Make sure you have all relevant contact details to hand in case you need them.
• Pay extra attention to your glucose control.
• If you do show flu-like symptoms (raised temperature, cough, difficulty breathing), it is important to consult a healthcare professional. If you are coughing up phlegm, this may indicate an infection so you should seek medical support and treatment immediately.
• Any infection is going to raise your glucose levels and increase your need for fluids, so make sure you can access a sufficient supply of water.
• Make sure you have a good supply of the diabetes medications you need. Think what you would need if you had to quarantine yourself for a few weeks.
• Make sure you have access to enough food.
• Make sure you will be able to correct the situation if your blood glucose drops suddenly.
• If you live alone, make sure someone you can rely on knows you have diabetes as you may require assistance if you get ill.

COVID-19 is a new coronavirus. The situation is not fully clear at this point, so keep informed of the latest developments. Look out for updates and advice from your government, national diabetes association and other reliable sources

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Study finds dopamine, biological clock link to snacking, overeating and obesity

Date:

January 3, 2020

Source:

University of Virginia

Summary:

A new study finds that the pleasure center of the brain and the brain's biological clock are linked, and that high-calorie foods -- which bring pleasure -- disrupt normal feeding schedules, resulting in overconsumption.

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Clock and eating concept (stock image).

Credit: © nehopelon / Adobe Stock

During the years 1976 through 1980, 15% of U.S. adults were obese. Today, about 40% of adults are obese. Another 33% are overweight.

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Coinciding with this increase in weight are ever-rising rates of heart disease, diabetes, cancer and health complications caused by obesity, such as hypertension. Even Alzheimer's disease may be partly attributable to obesity and physical inactivity.

"The diet in the U.S. and other nations has changed dramatically in the last 50 years or so, with highly processed foods readily and cheaply available at any time of the day or night," Ali Güler, a professor of biology at the University of Virginia, said. "Many of these foods are high in sugars, carbohydrates and calories, which makes for an unhealthy diet when consumed regularly over many years."

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In a study published Thursday in the journal Current Biology, Güler and his colleagues demonstrate that the pleasure center of the brain that produces the chemical dopamine, and the brain's separate biological clock that regulates daily physiological rhythms, are linked, and that high-calorie foods -- which bring pleasure -- disrupt normal feeding schedules, resulting in overconsumption. Using mice as study models, the researchers mimicked the 24/7 availability of a high-fat diet, and showed that anytime snacking eventually results in obesity and related health problems.

Güler's team found that mice fed a diet comparable to a wild diet in calories and fats maintained normal eating and exercise schedules and proper weight. But mice fed high-calorie diets laden with fats and sugars began "snacking" at all hours and became obese.

Additionally, so-called "knockout" mice that had their dopamine signaling disrupted -- meaning they didn't seek the rewarding pleasure of the high-fat diet -- maintained a normal eating schedule and did not become obese, even when presented with the 24/7 availability of high-calorie feeds.

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"We've shown that dopamine signaling in the brain governs circadian biology and leads to consumption of energy-dense foods between meals and during odd hours," Güler said.

Other studies have shown, Güler said, that when mice feed on high-fat foods between meals or during what should be normal resting hours, the excess calories are stored as fat much more readily than the same number of calories consumed only during normal feeding periods. This eventually results in obesity and obesity-related diseases, such as diabetes.

Speaking of the modern human diet, Güler said, "The calories of a full meal may now be packed into a small volume, such as a brownie or a super-size soda. It is very easy for people to over-consume calories and gain excessive weight, often resulting in obesity and a lifetime of related health problems.

"Half of the diseases that affect humans are worsened by obesity. And this results in the need for more medical care and higher health care costs for individuals, and society."

Güler said the human body, through thousands of years of evolution, is hard-wired to consume as much food as possible as long as it's available. He said this comes from a long earlier history when people hunted or gathered food and had brief periods of plenty, such as after a kill, and then potentially lengthy periods of famine. Humans also were potential prey to large animals and so actively sought food during the day, and sheltered and rested at night.

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"We evolved under pressures we no longer have," Güler said. "It is natural for our bodies as organisms to want to consume as much as possible, to store fat, because the body doesn't know when the next meal is coming.

"But, of course, food is now abundant, and our next meal is as close as the kitchen, or the nearest fast-food drive-through, or right here on our desk. Often, these foods are high in fats, sugars, and therefore calories, and that's why they taste good. It's easy to overconsume, and, over time, this takes a toll on our health."

Additionally, Güler said, prior to the advent of our electricity-powered society, people started the day at dawn, worked all day, often doing manual labor, and then went to sleep with the setting of the sun. Human activity, therefore, was synchronized to day and night. Today, we are working, playing, staying connected -- and eating -- day and night. This, Guler said, affects our body clocks, which were evolved to operate on a sleep-wake cycle timed to daytime activity, moderate eating and nighttime rest.

"This lights-on-all-the-time, eat-at-any-time lifestyle recasts eating patterns and affects how the body utilizes energy," he said. "It alters metabolism -- as our study shows -- and leads to obesity, which causes disease. We're learning that when we eat is just as important as how much we eat. A calorie is not just a calorie. Calories consumed between meals or at odd hours become stored as fat, and that is the recipe for poor health."

The National Institute of General Medical Sciences and University of Virginia Brain Institute funded the research.

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Story Source:

Materials provided by University of Virginia. Note: Content may be edited for style and length.

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